9713

• UCREFRP Catalog Number: 9713
• Author: VanHaverbeke, D.R.
• Title: Stock assessment and fisheries monitoring activities in the Little Colorado River within Grand Canyon during 2004.
• USFW Year: 2005.
• USFW - Doc Type: U.S. Fish and Wildlife Service
• Copyright Material: NO

Excluding all HBC ~ 150 mm, a nearly equal proportion of adult HBC (~ 200 mm)
were captured during the May trip (273 fish; 65%) compared to the April trip (206
fish; 66%). A small cohort of HBC ~ 75 mm was detected during the April trip (82
fish, 6.5% of the total catch), and during the May trip (96 fish; 3.7% ofthe total
catch).

Cumulative length frequencies for HBC (Figure 6) show relative uniformity in
length distribution between camps, with Boulders and Coyote capturing a slightly
higher proportion of fish < 100 mm on both trips.

Flannelmouth sucker length frequency distributions show a similar pattem to
HBC in that a greater number of fish were captured during the May trip (166 fish;
3% of total May fish captures) than during the April trip (88 fish; 5% of total April
fish captures), and that a small age-O cohort was detected during the May trip
(Figure 7). Most f1annelmouth sucker were captured in the Boulders (79%) and
Coyote (14%) reaches (Table 4).

Bluehead sucker length frequency distributions were much the same as HBC
and flannelmouth sucker length frequencies in that a greater number of fish were
captured during the May trip (481 fish; 10% of total May fish captures) than
during the April trip (98 fish; 5% of total April fish captures), and that a clearly
visible age-O cohort was observed during the May trip (Figure 8).

Sexual Condition

During the April trip, 36 ripe HBC were captured. Thirty-one ofthese fish were
male (TL range = 105 to 386 mm) and were captured between 0.9 and 12.07
rkm. The remaining five females (TL range = 148 to 364 mm TL) were captured
between 1.5 and 6.57 rkm. One ripe male fJannelmouth sucker (TL = 327 mm)
was captured at 1.25 rkm. Forty ripe bluehead sucker were captured. Thirty-four
of these were male (TL range = 176 to 282 mm) and were captured between 0.9
and 9.34 rkm. Six were female (TL range = 168 to 270 mm) and were captured
between 2.02 and 9.34 rkm.

During the May trip, 83 ripe HBC were captured. Only one of these was female
(TL = 404 mm), captured at 1.25 rkm. The other 82 males (TL range = 147 to
427 mm) were captured between 1.25 and 13.54 rkm. Ten ripe flannelmouth
sucker were captured (TL range = 460 to 525 mm). All were captured between
2.0 and 4.1 rkm, except one female captured at 10.4 rkm. In addition, eighty ripe
bluehead sucker (TL range = 127 to 316 mm) were captured between 0.1 and
11.7 rkm. Sixty-two of these fish were males.

During April, 22 HBC ~ 200 mm were ripe out of a total of 206 HBC ~ 200 mm
captured (Le., 11 % of the captured adult population in April was ripe). During
May, 63 HBC ~ 200 mm were ripe out of a total of 273 HBC ~ 200 mm captured
(Le., 23% of the captured adult population was ripe).

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